【摘要】：在石油工業(yè)和油氣田勘探開發(fā)領(lǐng)域中,研制新型光纖傳感器,建立完整的光纖傳感網(wǎng)絡(luò)系統(tǒng),實時監(jiān)測溫度、壓力、振動等諸多地質(zhì)物理量,對于油氣藏精細(xì)描述,提高油氣資源勘探開發(fā)效率十分重要。然而,光纖傳感器目前仍面臨著集成化、多參量測量以及系統(tǒng)的分布式、網(wǎng)絡(luò)化傳感等諸多方面的挑戰(zhàn)。基于光纖布拉格光柵(Fiber Bragg Grating, FBG)波長編碼型的光纖傳感器,具有體積小、重量輕、抗電磁性、遠(yuǎn)距離傳輸能力和抗腐蝕性等優(yōu)點,并且具備波長可復(fù)用性和多參量敏感性,在分布式傳感領(lǐng)域具備極強的優(yōu)勢和廣泛的應(yīng)用前景。本論文研究了新型光纖FBG的傳感機理,研制了多種新型光纖FBG傳感器,對每種傳感器的制作原理、傳感特性做了深入研究。具體研究內(nèi)容包括：1.概述了光纖波導(dǎo)和光纖FBG的模式耦合理論,對比了幾種非對稱結(jié)構(gòu)的光纖FBG,包括傾斜光纖FBG、長周期光纖FBG和局部寫入光纖FBG等,介紹了幾種常用的FBG刻寫技術(shù)；2.研制了三種基于“傳感結(jié)構(gòu)的特殊設(shè)計”的標(biāo)準(zhǔn)FBG彎曲、振動傳感器。(1)制作了一種基于組合式杠桿結(jié)構(gòu)的雙FBG光纖加速度傳感器。兩只FBG沿著桿上下對稱固定。當(dāng)感受到外界振動時其布拉格波長沿相反方向偏移。實驗測試結(jié)果顯示由于等截面量具有極強的橫向抗干擾能力,再加上L型剛性杠桿可實現(xiàn)外界振動信號的有效放大,測得該傳感器的靜態(tài)彎曲靈敏度為4.58nm/mm,動態(tài)靈敏度高達218.4pm/G。(2)利用金屬波紋管的高彈性,制作了一種芯軸式的FBG三維加速度傳感器,將質(zhì)量塊位于三維空間的中心位置,利用彈性金屬波紋管沿質(zhì)量塊各個面對稱固定,作為FBG與質(zhì)量塊連接的緩沖介質(zhì)。測試過程中對其中三只位于不同軸向的光纖FBG耦合輸出至檢測元件,驗證了傳感器對三維空間振動的方向依賴性。(3)研制了一種基于彎曲非等截面梁的光纖FBG傳感器,用一個半孔型的梁作為彎曲結(jié)構(gòu),其自由端用作慣性質(zhì)量塊來感受外界沿縱軸的位移和振動。經(jīng)過模擬得到半孔梁的應(yīng)變沿軸向為非均勻線性增加,因此隨著形變量的增加在其表面的FBG實現(xiàn)了布拉格(Bragg)光譜展寬和峰值波長的漂移。實驗中通過對光譜功率和峰值波長同時檢測,得到了其縱向彎曲和溫度的區(qū)分靈敏度分別為1.9dBm/mm和11.85pm/℃。進一步測試了傳感器的振動響應(yīng),得到該傳感器的共振頻率為250Hz,振動響應(yīng)范圍為0到3.5G。3.基于“光柵結(jié)構(gòu)的特殊設(shè)計”,利用紫外曝光技術(shù)寫制了一種新型的離軸型單模光纖光柵。寫柵過程中將光纖平行偏移激光光路一定程度使得照射在光纖上的衍射條紋沿光柵橫截面為部分曝光。制成的離軸FBG包層模式被有效耦合出纖芯,其中一些低階包層模式對彎曲具有方向相關(guān)性。利用離軸FBG作為全光纖型彎曲傳感器,實現(xiàn)了二維空間的矢量測量。彎曲靈敏度最高可達1.25dB/m~(-1),曲率范圍為0到lm~(-1)。并分別測量了彎曲傳感器對周圍環(huán)境的溫度和折射率交叉靈敏度,驗證了傳感器的溫度、折射率不相關(guān)性。4.通過對傾斜光纖FBG (Tilted FBG, TFBG)傳輸光譜中的共振模式加以理論分析和軟件模擬,制作了兩種基于TFBG的全光纖型傳感器。(1)刻寫了兩只傾斜角度為2° TFBG, Bragg波峰距離控制為20nm有利于在光譜透射窗口中同時檢測到各TFBG的共振譜信息。利用這兩只TFBG制作成一個三維形變光纖傳感器。傳感器的空間形變測試結(jié)果表明,在彎曲曲率從0m~(-1)到3m~(-1)范圍內(nèi),可實現(xiàn)空間的彎曲定標(biāo)測量(彎曲不確定為士180°)。彎曲靈敏度依據(jù)方向不同從-0.33dB/m~(-1)變化至+0.21dB/m~(-1)。第三維方向的軸向應(yīng)變靈敏度為1.06pm/με。且沿軸向的第三維空間可通過應(yīng)變和溫度波長區(qū)分測量。該傳感器結(jié)構(gòu)緊湊,總長度少于3cmm,且實現(xiàn)了三維空間的一體式測量。(2)討論了表面等離子體共振(SPR)傳感器的原理和傳感特點及TFBG鍍膜激發(fā)SPR的優(yōu)點�；赥FBG的光柵傾斜平面的方向性以及模擬所得的具有等離子體特性的高階包層模的模場能量分布特性,設(shè)計了一種更為簡單的TFBG鍍膜方式,優(yōu)化了光柵表面SPR的耦合效率。對傳感器在鹽溶液中的響應(yīng)加以驗證,并進一步在微小折射率擾動溶液中測量SPR共振峰處的能量變化,通過能量差分運算得到折射率靈敏度高達3.34×10~4dB/RIU。結(jié)果表明,通過定向單面涂覆金層可實現(xiàn)SPR的高效率激發(fā),大大降低SPR傳感器的制作的復(fù)雜性。
[Abstract]:In the field of petroleum industry and oil and gas field exploration and development, a new type of optical fiber sensor is developed, and a complete optical fiber sensing network system is established to monitor the temperature, pressure, vibration and other geological physical quantities in real time. It is very important for the fine description of oil and gas reservoirs and to improve the exploration and development efficiency of oil and gas resources. However, the optical fiber sensor is still facing the challenges of integration, multi-parameter measurement and distributed and networked sensing of the system. The optical fiber sensor based on the fiber Bragg grating (FBG) wavelength coding type has the advantages of small volume, light weight, electromagnetic resistance, long-distance transmission capability and corrosion resistance and the like, And has strong advantages and wide application prospect in the field of distributed sensing. In this paper, the sensing mechanism of a new type of FBG is studied, and a variety of new FBG sensors are developed. The manufacturing principle and the sensing characteristics of each sensor are deeply studied. The specific research contents include:1. In this paper, the mode-coupling theory of the fiber-optic waveguide and the fiber-optic fiber Bragg fiber (FBG) is summarized, and the optical fiber FBG of several asymmetric structures is compared, including the oblique optical fiber FBG, the long-period fiber FBG and the local write-in fiber FBG, etc., and several commonly used FBG etching techniques are introduced. Three "The special design of the sensing structure"-based standard FBG bending and vibration sensors have been developed. (1) a dual FBG fiber acceleration sensor based on a combined lever structure is manufactured. The two fbg are symmetrically fixed along the upper and lower sides of the rod. The bragg wavelength is offset in the opposite direction when the outside vibration is felt. The results show that the static bending sensitivity of the sensor is 4.58 nm/ mm and the dynamic sensitivity is up to 218.4 pm/ G. And (2) using the high elasticity of the metal corrugated pipe, a core shaft type FBG three-dimensional acceleration sensor is manufactured, the mass block is positioned in the center position of the three-dimensional space, and the elastic metal corrugated pipe is fixed along each surface of the mass block and is used as a buffer medium for connecting the FBG and the mass block. In the test, three optical fiber FBG sensors, which are located in different axial directions, are coupled and output to the detection element, and the direction dependence of the sensor on the three-dimensional space vibration is verified. (3) An optical fiber FBG sensor based on a curved non-uniform cross-section beam is developed, and a half-pass beam is used as a bending structure, and the free end of the beam is used as an inertia mass block to sense the displacement and vibration of the outside along the longitudinal axis. The strain of the semi-porous beam is increased linearly in the axial direction through the simulation, so the Bragg (Bragg) spectral broadening and the peak wavelength shift are realized with the increase of the shape variable on the surface of the FBG. By simultaneous detection of the spectral power and the peak wavelength, the sensitivity of the longitudinal bending and the temperature was 1.9 dBm/ mm and 11.85 pm/ 鈩，

本文編號：2465530